Minimally invasive endoscopic surgeries and techniques are widespread in the medical world today due to the obvious benefits of reduced patient trauma and recovery times. These procedures typically involve making one or more incisions in the patient in proximity to the surgical target, and inserting a cannula or other surgical port through which the entire surgery is preformed by manipulating endoscopic instruments within the port. Many endoscopic surgical procedures require removing or excising body tissue or other matter (such as a tumor) having a size greater than the diameter of the cannula. To accomplish this, the tissue must be cut into small enough pieces, or otherwise reconfigured to enable it to be removed through the cannula. Tissue morcellators are a well known means by which to accomplish this result. U.S. Pat. Nos. 5,439,474, 5,443,472, 5,520,634, 5,562,694, 5,569,927, 5,879,358, 6,039,748, 6,193,715 and 6,468,228, all describe tissue morcellators of varying complexity that can be used to morcellate and/or extract tissue from an endoscopic surgery site. These instruments generally consist of a pistol-style handle 102 (see FIG. 1) with an elongate shaft 106 for endoscopic access. The distal tip of the shaft is equipped with a rotary cutting mechanism 100 for cutting tissue that comes into contact with it. The handle either possesses a motor or provides connection to an external motor for rotating the cutting mechanism at the end of the elongate shaft. The shaft of the instrument is completely hollow and equipped at the proximal end with an entryway to allow passage of a grasper or tenaculum 104 into the surgical site for the purpose of grasping (FIGS. 2a and 2b), pulling and guiding tissue into contact with the cutting element, and eventually removing the cut tissue out through the shaft (FIG. 2c). This entryway is generally equipped with one or more gaskets that seal to the shaft of the tenaculum when it is in use to preclude the loss of pneumoperitoneum.
Although functional, these devices are limited in that they are generally complex, expensive, and rely solely on sharp edges and other mechanical means (electric motors, mechanical screws) to cut tissue. Reliance on such mechanical means and sharp shearing surfaces is sub-optimal in that device performance will degrade as the edge dulls with use. In addition, sharp cutting edges present the risk of accidental tissue cutting or damage and provide no hemostatic capability. Another deficiency of these devices arises from the weight of the integral motors or drive cables required to couple the instrument to an external motor, which makes manipulation of the instrument both awkward and fatiguing.
Alternative mechanisms and devices for endoscopically cutting or dissecting tissue within the body have been developed. For example, U.S. Pat. Nos. 5,697,281, 5,697,536, 5,697,882, and 5,697,909, which are incorporated herein by reference in their entirety, describe bipolar electrosurgery technology that uses a plasma/vapor pocket to provide rapid tissue vaporization or cutting with reduced collateral tissue damage and improved hemostatic effect as compared to monopolar electrosurgery. These patents describe a custom generator which is capable of forming and maintaining this plasma bubble in a conductive fluid media, such as normal saline, and a collection of electrodes which can be used to cut and vaporize tissue. None of these devices, however, are morcellators, as none are designed to or capable of being used to excise and remove relatively large tissue volumes from the body.
Accordingly, there remains a need for an improved morcellator that provides rapid and efficient cutting and concomitant hemostasis without the need for sharp edges and mechanical drive mechanisms.